Evaluation on the mixing state of solid-liquid two-phase in stirred tank via an improved Voronoi diagram approach

Abstract

In hydrometallurgical leaching of zinc-containing solid wastes, the poor performance of the solid-liquid two-phase mixing process could result in significant energy wastage. It was necessary to realize the assessment of the solid-liquid two-phase mixing state in the stirred tank to provide data support for the mixing process enhancement. In this work, the boundaryless problem of the traditional Voronoi diagram was solved by reconfiguring the boundary through virtual points, and a mixing uniformity assessment method was proposed in combination with the coefficient of variation method. Meanwhile, the mapping of image pixels to Voronoi cells was established, breaking through the limitation that the traditional camera technique could only be used for surface measurements, and realizing point measurements of solid-phase concentration distribution relationships. The evaluation results show that the uniformity of the four images with normal, circular, concentrated and Poisson distributions were 1.87, 1.50, 4.38 and 0.61, respectively. The uniformity of the mixing images for the similar model at the moments of 6.4, 10 and 11 s were 1.51, 1.25 and 0.38, respectively. The present method was very sensitive to the variation of the solid-phase distribution. Point measurements enabled qualitative and quantitative analysis of the spatial and temporal characteristics of particle concentrations. Qualitative analyses help to visualize changes in mixing conditions. The quantitative analysis helps to target improvements in the mixing process. In addition, the method could be extended to analyze flow and mixing processes with discrete geometrical features.